Hello,

Here another question I asked on the beginners list with no answers.

Chapter 4 of RealWorldOcaml begins with this programm :

open Core.Std

let build_counts () =
     In_channel.fold_lines stdin ~init:[] ~f:(fun counts line ->
           let count =
               match List.Assoc.find counts line with
                 | None -> 0
                 | Some x -> x
           in List.Assoc.add counts line (count + 1) )

let () = build_counts ()
  |> List.sort ~cmp:(fun (_,x) (_,y) -> Int.descending x y)
  |> (fun l -> List.take l 10)
  |> List.iter ~f:(fun (line,count) -> printf "%3d: %s\n" count line)

But I do not really understand what each line does

1) What means ln.channel.fold_lines stdin ~init part means ?
2) What does the |> does exactly.  I know chapter 2 does explain it a little bit but it's still not clear to me
3) What does ~cmp mean.

Roelof